Think about it this way, if you're a dealer you want to inflate your supply right? So, if you have a street drug that is an 'upper' and you want to cut it, you need to cut it with uppers, or something that can mask an upper. That cut needs to blend in, if you're expecting something blue, and it has red in it, then you'll know its off.
Psychedelics would need to be cut with other psychedelics, but it's not as easy as mixing two things and having it come out. LSD comes as a crystal and is then put in an alcohol solution and dried on paper, there's not many things that would work that way. If the goal is to stretch your supply, you just further dilute it, and many people do.
Where there are cheaper/easier alternatives are things in the 2c family, or others that are _close_ to the experience of LSD but not, and are also more toxic.
I don't know if any of that is clear, or makes sense but